Method of manufacturing a component of a rotary machine and component manufactured using said method

ABSTRACT

A method of manufacturing a component of a rotary machine, the component has at least one inner passage that extends from a center up to a boundary surface of the component and is at least partly closed, and a blank is provided that includes the boundary surface and a top surface. The Method includes a first subtractive machining step that is carried out in which a part of the passage that at least includes an opening of the passage into the boundary surface as well as a cut-out in the top surface are manufactured by machining production, and subsequently the passage is completed by build-up production on the blank.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to European Application No. 16172289.7,filed May 31, 2016, the contents of which are hereby incorporated hereinby reference.

BACKGROUND Field of the Invention

The invention relates to a method of manufacturing a component of arotary machine and to a component of a rotary machine.

Background of the Invention

In the manufacture of rotary machines such as pumps, turbines,compressors, compactors or expanders, it is known to work rotatingrotors, pump wheels, impellers and stationary diffusers or guide wheelsas components out of blanks by cutting or machining processes, forexample by milling. In this respect, the blank can be present as solidmaterial or can already be pre-worked by a primary shaping process.

Such a method is known, for example, from EP-B-2 012 957. The methodproposed there is in particular characterized in that it allows acutting manufacture of the component, by which it is meant that thecomponent as a whole is at least substantially brought into the desiredend shape from the blank by a cutting apparatus. The joining together ofprefabricated elements of the component, for example by welding, is nolonger necessary with such an integral manufacture. This is inparticular advantageous because weld seams or other connection pointsrepresent a weak point at heavily loaded parts of the component in theoperating state that can be the cause of a crack or of different damage,for example caused by corrosion, to the component.

A cutting manufacture is thus in particular possible with highly loadedcomponents without the joining together of individual elements. Suchcomponents as rotors (impellers) of pumps, for example, are thereforeproduced from solid material, depending on the application e.g. fromhigh-strength stainless steels, super alloys, other suitable metals ormetal alloys or also from non-metallic materials, for example ceramicmaterials, and the blades and channels of the impeller are worked out ofthis material by cutting machining, e.g. by milling.

As is also already shown in EP-B-2 012 957, however, a total cuttingmanufacture of the component is sometimes not possible for purelygeometrical reasons. This can be the case, for example, when theimpellers are configured as covered or closed impellers. With such anembodiment, the impeller comprises a hub plate on which the blades arearranged and furthermore comprises a top plate that covers the blades ontheir side remote from the hub plate fully or at least partly. At leastpartly closed passages are thus formed between the blades andrespectively extend from the center of the impeller up to its outerradial boundary surface.

SUMMARY

Even if it is considered that these passages can be milled or machinedfrom the blank in a cutting process from both sides, that is from theinner space of the impeller and from its radial boundary surface, usinga cutting apparatus, it is clear that the geometry sets limits here andmakes a total cutting manufacture impossible in many cases.

In such cases in which it is also no longer possible or practical forpurely geometrical reasons to mill the impeller in total in one piece ofsolid material, it is therefore prior art first to work the hub plateand the blades out of the blank in a cutting manner. The passagesbetween the blades are then open passages that can be manufactured in asimple manner. The top plate is subsequently placed on and is joined,for example welded, to the hub plate or to the blades. The weld seams orthe join points then respectively extend where the blades come intocontact with the top plate. However, this brings about the disadvantagethat the loads are particularly high or critical at just this point inthe operating state. This border region between the blades and the topplate is particularly prone to joining defects that are sometimes noteven noticed during the manufacture.

It is alternatively also known to produce the regions of the passages nolonger accessible to milling using an eroding process, for example sparkerosion (EDM: electrical discharge machining). These methods are,however, comparatively slow and cost-intensive as a rule.

It is also prior art to manufacture such components having innerpassages in a technical molding manner, wherein the inner passages arethen produced by a corresponding embodiment of the mold or of thecasting cores. A cast component has the disadvantage, however, thatdefects in the structural conditions may occur during molding, forexample, that have a negative effect on the load capacity or on thestability of the component. As a rule, the achievable surface qualitiesand the dimensional accuracies of the regions no longer accessible tomilling are furthermore limited in the molding process.

A method for the cutting manufacture of a closed impeller is thereforeproposed in EP-A-2 669 042 in which the component to be produced(impeller) is divided into two sub-volumes that are adjacent to oneanother at an interface. In this respect, the sub-volumes are fixed suchthat the interface does not include or cut any of the boundary surfacesof the passages and such that the passages as a whole can be worked outof the first sub-volume that later comprises the complete passages by acutting method, e.g. milling. The second sub-volume, that is then onlypart of the top plate, is either manufactured as a separate element andis joined to the first sub-volume after the completion of the passagesor the second sub-volume is built up on the first sub-volume by adepositing machining method, for example by deposit welding. It shouldhereby be made possible, on the one hand, to produce the passagescompletely by a cutting manufacture and it should be avoided, on theother hand, that the interface intersects or bounds the passages suchthat no join defects can occur between the blades and the top plate.This method is, however, also still subject to geometrically causedlimits.

This problem explained with reference to closed impellers is, however,also present with other components that have an inner passage whoseposition or geometry is such that a total cutting manufacture is inparticular not possible or not practical for geometrical reasons. Closedstators, diffusers or also cooling passages, for example for coolingair, in turbine blades, can be named as examples here.

Starting from this prior art, it is therefore an object of the inventionto provide a different method of manufacturing a component of a rotarymachine that has at least one inner passage, by which method inparticular those components can also be manufactured that do not allowany total cutting manufacture of the passage for geometrical reasons,wherein the method should enable a high reliability of the component inthe operating state. A corresponding component should furthermore beprovided by the invention.

The subjects of the invention satisfying this object are characterizedby the features described herein.

In accordance with the invention, a method is therefore provided formanufacturing a component of a rotary machine, which component has atleast one inner passage that extends from a center up to a boundarysurface of the component and is at least partly closed, wherein a blankis provided that comprises the boundary surface and a top surface,wherein a first subtractive machining step is carried out in which apart of the passage that at least comprises an opening of the passageinto the boundary surface as well as a cut-out in the top surface ismanufactured by cutting production, and wherein subsequently the passageis completed by build-up production on the blank.

The method in accordance with the invention thus advantageously combinesa subtractive machining in which material is removed from the blank withan additive or build-up manufacturing or machining in which material isdeposited. In this respect, only a part of the passage is manufacturedby a cutting production, whereas the remainder of the passage isgenerated by a build-up production. It is possible by this combinationto generate a passage having—at least almost—any desired geometry.

Since the blank does not have to be manufactured in a technical castingprocess, the blank can advantageously comprise a forged material that isthen machined in a cutting process. All the advantages of the forgedmaterial are maintained by the cutting machining. In this respect, atleast the opening of the passage into the boundary surface of thecomponent is manufactured in a cutting process in the first subtractivemachining step. With a component of a rotary machine, for example with aclosed impeller, this opening or the walls bounding it is/are typicallythat region that is exposed to the greatest loads by the flowing fluidin the operating state. With the impeller of a pump, this regioncomprises the outlet edge of the blade that bounds the inner passagethat is flowed through by the fluid. It is known that the greatestmechanical or hydrodynamic loads occur at the outlet edge of the bladein the operating state with the impeller of a pump. Since this openingof the passage is manufactured in a cutting process, all theadvantageous properties of the forged material which the blank comprisesare maintained. The region of the opening is thereby characterized by aparticularly high mechanical load capacity and stability. Such machiningprocesses such as welding that bring about a high heat input into thematerial that could have a negative effect on the properties and on thestructural conditions can in particular be dispensed with at theopening.

In addition, in the first subtractive machining step, a part of thepassage is manufactured in a cutting process as a cut-out in the topsurface of the blank, with this part being connected to the opening ofthe passage into the boundary surface. Only a part of the passage thatstarts as a recess in the top surface of the blank and extends up to theopening in the boundary surface is thus completed after the end of thefirst subtractive machining step. In this respect, the first subtractivemachining step can comprise either a milling from the boundary surfaceor a milling from the top surface of the blank. It is naturally inparticular also possible that the first subtractive machining stepcomprises both a milling or a cutting machining from the top surface anda milling from the boundary surface.

Once the first subtractive machining step has ended, the passage iscompleted by a build-up production and the component is brought into itsfinal shape.

The cut-out in the top surface is preferably produced in the firstsubtractive machining step such that it extends up to the center wherethe passage starts. Since the top surface of the blank is freelyaccessible to a cutting apparatus, it is advantageous to configure thepassage as a cut-out in the top surface up to its end disposed at thecenter in the first subtractive machining step. However, this does notmean that the passage is thereby completed. The region of the passageclose to the center is then only configured as a cut-out in the topsurface and not yet as a closed or inner passage. The base surface ofthe passage and, optionally, parts of its lateral boundary walls aregenerated by this cutting machining while the completion is only madesubsequently by the build-up production.

In a preferred embodiment, the component comprises a plurality of innerpassages of which each extends out of the center up to the boundarysurface, wherein adjacent passages are each separated by a partitionwall, wherein a respective part of the passage is manufactured in thefirst subtractive machining step of each passage, said part at leastcomprising an opening of the passage into the boundary surface and acut-out in the top surface, and wherein each partition wall is onlycompleted by the build-up production. It is particularly preferred inthis respect if the opening of each passage into the boundary surface isconfigured in the first subtractive machining step such that the openingof the respective passage is already configured as covered or closed bythe top surface of the blank. The openings then respectively representopenings in the boundary surface bounded at all sides.

The blank is preferably a solid body, and in particular a rotationallysymmetrical body, i.e. the blank has no inner cavities. A cylindricalaxial and continuous bore can, however, preferably be provided in thecenter of the blank and serves, for example, to fix the completedcomponent to a shaft, e.g. to the drive shaft of a pump. I.e. the topsurface of the blank preferably has at most one central opening beforethe first subtractive machining step that is arranged radially inwardlydisposed such that each start of a passage disposed at the center isseparated from the central opening by a ring body in the completed stateof the component.

In accordance with a particularly preferred embodiment, the firstsubtractive machining step is carried out such that the top surface ofthe blank has a contiguous, ring-shaped region after its completion thatis adjacent to the boundary surface and that covers all the openingssuch that all the openings are already configured as closed parts of therespective passages. This means that all the openings of the passagesand the walls respectively bounding them are already manufactured in theend shape of the component to be manufactured in the first subtractivemachining step. This has the advantage that those opening regions of thepassages that are exposed to the highest strains in the operating statehave a particularly high load capacity and thus also a high reliabilityin operation because these opening regions are manufactured in a purelycutting process and are thus not exposed to any high heat input in theproduction process such as would, for example, be caused by welding,thermal injection or other methods.

The build-up production preferably takes place layer-wise. It ispossible in this respect that each layer is oriented perpendicular to anaxial direction. It is naturally also possible to apply the layers inother alignments, that is such that the respective surface normal of thelayer is aligned obliquely to the axial direction. This means that theadditive build-up on the blank takes place after the end of the firstsubtractive machining step by a successive application of materiallayers until the component is completed. The application of layers takesplace in a preferred variant such that the individual layers arerotationally symmetrical. This is in particular also possible when thelayers are oriented perpendicular to the axial direction, but also on alayer application in which the individual layers are oriented obliquelyto the axial direction.

A further preferred measure comprises the build-up production comprisesa plurality of additive machining steps to successively build up thecomponent.

It is particularly preferred if at least one further subtractivemachining step is carried out between the additive machining steps. Thestructure built up in the preceding additive machining step can then bereworked e.g. by milling, grinding or polishing in this furthersubtractive machining step. A surface optimization or a particularlyfaithful geometry can be achieved by this measure.

It is especially preferred that a respective further subtractivemachining step is carried out between two additive machining steps. Thismeans that the additive machining steps and the further subtractivemachining steps are carried out alternately. This allows a particularlyhigh precision and surface quality of the component to be produced.

Machining apparatus are known today with which both additive productionprocesses, for example laser build-up welding, and subtractiveproduction processes, for example milling or grinding, can be carriedout. Such apparatus, for example, have different machining heads thatcan be automatically exchanged, with one machining head being configuredfor laser build-up welding, for example, while another machining head isconfigured for milling. Exactly such machining apparatus allow a fastand problem-free change between subtractive and additive machiningprocesses without the workpiece to be machined having to be reclamped ortransferred into another machining station for this purpose. This allowsa particularly fast, inexpensive and high-quality manufacture ofcomponents that are produced in a very precise manner.

A further preferred measure comprises the component being built upelement by element after the first subtractive machining step, withinitially only each partition wall preferably being completed. All thepartition walls are thus, for example, first completely built up betweenthe passages after the end of the first subtractive machining step andthe still missing parts are only subsequently built up, e.g. those partsthat turn the passages into closed passages.

It is particularly preferred for technical process reasons if thebuild-up production is carried out with the aid of a laser.

Applications that are particularly relevant to practice are when thecomponent is configured as a impeller, as a stator or as a diffuser of arotary machine, in particular of a pump, of a turbine, of a compressor,of a compactor or of an expander.

A component of a rotary machine is furthermore provided by the inventionthat is manufactured in accordance with a method in accordance with theinvention.

In accordance with a preferred embodiment, each partition wall isconfigured as a blade.

Applications that are particularly relevant to practice are when thecomponent is configured as a impeller, as a stator or as a diffuser of arotary machine, in particular of a pump, of a turbine, of a compressor,of a compactor or of an expander.

Further advantageous measures and embodiments of the invention resultfrom the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail hereinafter withreference to the drawings.

FIG. 1 is an axial sectional representation of an embodiment of a closedimpeller;

FIG. 2 is a perspective representation of an embodiment of a blank forthe carrying out of an embodiment of a method in accordance with theinvention;

FIG. 3 is a perspective representation of the blank of FIG. 1 after theend of the first subtractive machining step;

FIG. 4 is a perspective representation of an intermediate state duringthe build-up production; and

FIG. 5 is a perspective representation of the completed component thatis manufactured from the blank in accordance with FIG. 1 and FIG. 2.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The method in accordance with the invention serves for the manufactureof a component of a rotary machine, wherein the component has at leastone inner passage that extends from a center up to a boundary surface ofthe component and is at least partly closed. In this respect, a closedpassage means a passage that is completely closed with the exception ofan inlet or of an outlet, that is, is configured as tubular, that is thepassage is bounded everywhere by one or more walls perpendicular to itsmain direction of flow. Unlike this, an open passage means one that isnot bounded by a wall, but is open, in a direction perpendicular to itsmain direction of flow, that is in a direction perpendicular to itslongitudinal extent. A passage having a U-shaped or V-shaped wall isthus an open passage, for example. If the open side of the U section orof the V section were to be covered by a top, the passage would be aclosed passage.

A partly closed passage then means one that is configured partly as aclosed passage and partly as an open passage.

In the following description of the invention, reference is made withexemplary character to an example important for practice in which thecomponent is a closed or covered impeller (rotor) of a turbo-machine,e.g. of a pump. For a better understanding, FIG. 1 shows an axialsectional representation of an embodiment of a closed impeller that isprovided as a whole with the reference numeral 1 and that can bemanufactured by a method in accordance with the invention.

In the operating state, the impeller rotates about an axis of rotationthat fixes an axial direction A. A direction perpendicular to this axialdirection A is called a radial direction. FIG. 1 shows the impeller 1 ina sectional representation along the axial direction A. The impeller 1comprises in a manner known per se a hub plate 2 by which the impeller 1is typically mounted or fastened to an axle or shaft, not shown, as wellas furthermore a plurality of blades 3 that are arranged on the hubplate 2 and a top plate 4 that at least partly covers the blades 3 attheir side or edge remote from the hub plate 2. In this respect, the topplate 4 extends higher than the hub plate 2 in accordance with therepresentation (FIG. 1) with respect to the axial direction A. An innerspace 6 is thereby formed above the blades 3 in accordance with therepresentation that is bounded by the top plate 4 with respect to theradial direction. This inner space 6 represents the inlet through whicha fluid flows onto the impeller 1 in the operating state. A respectiveinner passage 7 that is configured as an at least partly closed passage7 and that is here configured as a closed passage is present between twoadjacent blades 3 and respectively extends from a center that is formedby the inner space 6 up to a boundary surface 42 of the impeller 1. Theboundary surface 42 represents the radially outer surface of theimpeller 1 that extends in parallel with the axial direction A, that isthe surface that bounds the impeller in the radial direction. Theboundary surface 42 comprises the radially outer surfaces of the topplate 4 and of the hub plate 2 as well as the radially outer end edgesof the blades 3 that are called outlet edges 31 (see FIG. 3).

It is naturally also possible in dependence on the embodiment of thecomponent that the end edges of the blades 3 are set back with respectto the radial direction, that is are not disposed in the boundarysurface 42. The top plate 4 and/or the hub plate 2 then project beyondthe blades 3 or beyond the end edges of the blades 3 with respect to theradial direction. Such an embodiment is in particular also possible withan impeller of a turbine in which the outer end edges of the blades 3typically represent the inlet edges.

Each of the closed passages 7 is thus surrounded by a boundary surface 8that is respectively composed of the mutually facing surfaces of twoadjacent blades 3 as well as of the interposed surface segments of themutually facing surfaces of the hub plate 2 and of the top plate 4. Theblades 3 therefore each form a partition wall between two adjacent innerpassages 7. Each passage 7 comprises an opening 71 with which it opensinto the boundary surface 42. Openings 71 adjacent in the peripheraldirection are each separated from one another by an outlet edge 31.

The impeller 1 additionally has a central axial bore 9 that serves forreceiving a shaft or an axle on which the impeller 1 can be mounted.

An embodiment of the method in accordance with the invention will beexplained in more detail in the following with reference to FIGS. 2-4. Ablank is first provided in accordance with the method in accordance withthe invention. FIG. 2 shows, in a perspective representation, anembodiment of such a blank which is designated as a whole by thereference numeral 10. The blank 10 comprises the boundary surface 42 aswell as a top surface 11 that bounds the blank 10 in the axial directionA.

The blank particularly preferably comprises a forged material that canbe a metal or a metal alloy. Steel in its known embodiments is thussuitable, for example, or aluminum, titanium, nickel, a nickel or cobaltbase alloy or a non-ferrous metal. Other forged materials are naturallyalso possible, for example a cast material, a plastic or a compositematerial or another cuttable material.

The blank 10 is configured as a solid body, that is in particularwithout inner cavities—apart from the optionally already present centralaxial bore 9. The blank 10 is in this respect manufactured or machinedsuch that it already comprises a part of the hub plate 2 as well as apart of the top plate 4, with these parts each being configured—apartfrom the passages—in their desired end shape or at least substantiallyin their end shape. “Substantially” in this context means thatpost-machining can naturally still be carried out at a later point intime, such as polishing, grinding or similar, but the substantial shapeis already completed with the blank 10.

The same also applies accordingly to the boundary surface 42. This isalso already in its end shape or substantially in its end shape apartfrom the openings 71 of the passages 7. This in particular means thatthe extent H of the boundary surface 42 in the axial direction A isalready the one that has the completed component. The top surface 11 canbe configured as a planar circular surface that is orientedperpendicular to the axial direction A and that optionally has a centralopening that is generated by the central axial bore 9.

In the embodiment described here, however, the top surface 11 is notconfigured as a planar surface. The top surface 11 comprises aring-shaped region 111 that is outwardly disposed with respect to theradial direction, that is adjacent to the boundary surface 42 and thatis preferably oriented perpendicular to the axial direction A. A region112 of a conical surface shape adjoins the ring-shaped region 111 in aradially inwardly disposed manner and forms an inwardly directed taper.A circular central ring region 113 adjoins the region 112 of conicalsurface shape in a radially inwardly disposed manner, surrounds thecentral axial bore 9 coaxially and is likewise oriented perpendicular tothe axial direction A. This means that the ring-shaped region 111 andthe central ring region 113 are coaxial, with the central ring region113 being lower with respect to the axial direction A in accordance withthe representation than the ring shaped region 111 and being connectedthereto via the region 112 of conical surface shape. The blank 10therefore has a recess in its top surface 11 overall.

It is naturally also possible that the ring-shaped region 111 or thecentral ring region 113 is not oriented perpendicular to the axialdirection. This can be advantageous, for example, on the production ofsemi-axial impellers.

Apart from the central opening, the top surface 11 is configured as acontiguous surface that has no further openings. The radially outwardlydisposed ring-shaped region 111 preferably forms a part of the top plate4 of the finished component 1.

The blank 10—as also shown in FIG. 2—is particularly preferablyconfigured as rotationally symmetrical with respect to the axialdirection A.

A first subtractive machining step is now carried out at this blank 10and will be explained in the following. FIG. 3 shows a perspectiverepresentation of the blank 10 after the end of the first subtractivemachining step. The first subtractive machining step is specificallycarried out by cutting production.

A subtractive machining step in this respect means that material isstripped or removed from the workpiece—here the blank 10—in such amachining step. A cutting production as generally customary means aproduction in which excess material is cut off from the blank 10 or fromthe workpiece in a form of chips to achieve a desired geometrical shape.Cutting production processes are, for example, milling, turning,drilling, planing, filing, grinding, honing or lapping, to name just afew examples.

The first subtractive machining step preferably comprises a milling by acutting apparatus that, for example, comprises a computer-controlledmilling tool. The cutting apparatus is particularly preferablyconfigured at least as a five-axis milling machine with which thedesired geometrical shape is worked out of the blank 10. The millingtool is typically guided by a manipulator, with the guidance takingplace in a computer-assisted manner.

In the first subtractive machining step, a part of each passage 7 ismanufactured that at least comprises the opening 71 of the passage 7into the boundary surface 42 as well as a cut-out 72 in the top surface11 of the blank. As FIG. 3 shows, the region of the opening 71 of thepassage 7 is in this respect configured as a closed passage section. Theopenings 71 are each milled into the boundary surface 42, with adjacentopenings 71 each being separated from one another by an outlet edge 31.The radially outwardly disposed ring-shaped region 111 of the topsurface 11 of the blank 10 in this respect covers each of the openings71 of the passages 7 such that all the passages 7 are closed by thering-shaped region 111. This means that, after the end of the firstsubtractive machining step (see FIG. 3), the top surface 11 of the blank10 comprises the ring-shaped section 111 that is adjacent to theboundary surface 42 and is configured as a ring-shaped contiguoussurface that has no opening, that is, is continuous with respect to theperipheral direction and that covers all the openings 71 of the passages7.

The cut-outs 72 that are produced in the top surface 11 of the blank,that is in the central ring region 113 and in the region 112 of conicalsurface shape in the embodiment described here, form still open passageregions of the passages 7 subsequently still to be completed after thisfirst subtractive machining step. Each cut-out 72 is milled such thatits base surface 81 already has substantially the final shape for thepassage 7, that is in particular also already comprises the geometricalextent of the respective passage 7.

Each cut-out 72 is preferably produced in the first subtractivemachining step such that it extends up to the center, here to the innerspace 6, where the passage 7 starts. Each cut-out 72 starts in aradially inwardly disposed manner spaced apart from the central openingthat is generated from the central axial bore 9, i.e. none of thecut-outs 72 is connected to or opens into this opening. Each start of apassage 7 disposed in the center—here the inner space 6—is thusseparated from the central opening of the bore 9 by a ring body 21. Inthe completed state, this ring body 21 forms a part of the hub plate 2.

The cut-outs 72 and the openings 71 are milled in the first machiningstep such that they are connected to one another, i.e. each cut-out 72merges into the region that comprises the respective opening 71 of theassociated passage 7.

After the end of the first subtractive machining step (see FIG. 3), theblank 10 therefore has the following shape: The opening 71 of eachpassage 7 is already configured at least substantially in the shape ofthe finished component 1 in the boundary surface 42 and is covered bythe ring-shaped region 111 of the top surface 11 of the blank 10. Therespective passage 7 extends from the respective passage 71 into theinterior of the blank 10 and merges into the respective cut-out 72 thatis open at the top in accordance with the illustration (FIG. 3) and thatextends up to the start of the respective passage 7 disposed at thecenter, with the base surface 81 of each cut-out 72 already at leastsubstantially having the configuration of the base surface of thefinished passage 7. While the passages 7 therefore are already in theirfinal shape or at least substantially in their final shape in the regionof their openings 71, the radially inwardly disposed region of eachpassage 7 that comprises the upwardly open cut-out 72 is still not yetcompleted in its final shape.

The same applies accordingly to the partition walls 3 that later formthe blades 3 of the impeller 1 and that each separate two adjacentpassages 7 from one another. In the region of the boundary surface 42,each partition wall 3 already has its final shape or at leastsubstantially final shape, that is the outlet edge 31 of each partitionwall 3 is in particular already completed and is at least substantiallypresent in its final configuration. In the radially inwardly disposedregion of the blank 10, the partition walls 3 are each only partlypresent; they are therefore not yet finished and in particular have notyet reached their final height with respect to the axial direction A.

It is understood that the first subtractive machining step can compriseboth a milling starting from the top surface 11 and a milling startingfrom the boundary surface 42. In this respect, it is advantageous formany applications if the cut-outs 72 are milled starting from the topsurface 11 and if the openings 71 are milled starting from the boundarysurface 42. Depending on the component 1, it is naturally also possiblethat machining only takes place in the first subtractive machining stepstarting from the top surface 11 or only starting from the boundarysurface 42 in a milled or cutting manner.

A particular advantage of the embodiment described here comprises inparticular the region of the openings 71 having the outlet edges 31disposed therebetween and the ring-shaped region 111 that covers theopenings 71 and that is part of the top plate 4 already being in theirfinal shape or at least substantially in their final shape after thefirst subtractive machining step. Particularly the outlet edges 31 andspecifically the interface between the outlet edges 31 and the top plate4 are the critical regions in which the highest loads occur in theoperating state and where crack formations, degradations or otherdisadvantageous wear or fatigue phenomena are most likely to occur.Since these critical regions can be manufactured with the aid of cuttingproduction processes in the method in accordance with the invention,they can be produced with an extremely high precision, on the one hand,and such production methods that bring about a very high heat input intothe material, e.g. welding or joining processes with which elements arepermanently connected, can be completely dispensed with in thesecritical regions, on the other hand. These methods with high heat inputcan namely result in joining defects or unwanted changes in thestructural conditions that have a negative effect on the load capacityof the component.

A further advantage of purely cutting production is that with a blank 10of a forged material, all the positive properties of the forged materialare maintained.

Once the first subtractive machining step is ended (see FIG. 3), thestill missing parts of the component 1 are manufactured by a build-upproduction and the component 1 is brought into its final shape. FIG. 5shows in a perspective representation the completed component 1, that ishere the covered impeller 1.

The build-up production comprises one or more additive machining steps.An additive machining step or an additive production that is also calledgenerative production, in this respect means a machining step in whichmaterial is applied to or deposited on the workpiece, that is the blank10 here. The desired structures are typically generated, e.g. bybuilding up on a workpiece, in an additive production from a formlessmaterial, for example liquids or powders, or also from a neutral-shapematerial, for example band-shaped or wire-shaped material, by chemicaland/or physical processes. Additive production methods for metallicmaterials known per se are, for example, build-up welding processes,specifically inert gas processes such as tungsten inert gas welding(TIG) or laser build-up welding or plasma processes or selective lasermelting (SLM).

Once the first subtractive machining step has therefore been ended, thestill missing regions of the component 1, they are in particular partsof the partition walls 3, parts of the cover for closing the passages7—that is in the embodiment described here parts of the top plate 4—andparts of the hub plate 2—are generated in build-up production.

The still missing region of the partition walls 3 (blades 3) and themissing regions of the top plate 4 and of the hub plate 2 are, forexample, generated by selective laser melting. In this method known perse, the material to be processed is applied to the blank 10 in a thinfilm in powder form. The powdery material is melted on locallycompletely by laser radiation and forms a solid material film after itssolidification. The blank 10 is subsequently lowered by the amount of alayer thickness and material is again applied in powder form that isthen again locally melted by laser radiation. This cycle is repeated forso long until the component 1 is completed. It is naturally possiblethat post-machining such as grinding, polishing or similar cansubsequently still take place.

In another preferred embodiment, the still missing parts are generatedin build-up production by laser build-up welding. The method of laserbuild-up welding with its different variants is sufficiently known tothe skilled person and therefore does not require any explanation here.

It is possible in this respect to carry out the build-up productionlayer-wise and in particular while utilizing the rotationallysymmetrical configuration of the blank 10.

It is another likewise preferred embodiment to build up the component 1element by element in build-up production, i.e. the individual elementsof the component 1 such as the partition walls 3 or the covers of thepassages 7 are successively built up in the sense that first oneelement, e.g. the partition walls, is built up completely up to its endstate and subsequently the next element is completely built up. Thisprocess is repeated for so long until the component is completed.

It is furthermore possible that the individual elements of the component1 are not built up completely, but rather only partly, that is first onepart of the partition walls 3 is built up, then a part of the covers ofthe passages 7, then again a part of the partition walls 3, etc. In thisrespect, a further subtractive machining step can preferably be carriedout after a partial build-up.

FIG. 4 shows as an example in a perspective representation anintermediate state of such a build-up production in which the component1 is built up element by element. In this example, after the end of thefirst subtractive machining step, all the still missing regions of thepartition walls 3, that is here the blades 3 of the impeller 1, arefirst built up. FIG. 4 shows the impeller 1 in an intermediate state ofbuild-up production in which the blades 3, that is the partition walls 3between adjacent passages 7, as well as the hub plate 2 are just builtup completely, i.e. in their final form. Subsequently, the still missingregion of the top plate 4 is then built up by build-up production inorder thus to complete the impeller 1. This completed impeller 1 isshown in FIG. 5.

As already mentioned, in accordance with a preferred embodiment, thebuild-up production can comprise a plurality of additive machining stepsto successively build up the component 1. It is particularly preferredin this respect if at least one further subtractive machining step iscarried out between the additive machining steps.

In such a further subtractive machining step, deviations from thedesired geometry that have arisen in the preceding additive machiningstep can, for example, be compensated by cutting production. Millingwork or grinding work can thus be carried out in this furthersubtractive machining step to strip such material of which too much wasdeposited in the additive machining step or to level, to grind or tosimilarly treat transitions between adjacent layers.

It is particularly preferred if a respective further subtractivemachining step is carried out between two additive machining steps, i.e.the additive machining steps and the further subtractive machining stepsare carried out alternately or alternatingly. A particularly highquality and precision of the component 1 can herewith be ensured.

Modern machining tools are known today with which both subtractivemachining steps and additive machining steps can be carried out in thesame machining chamber without it being necessary in so doing to reclampthe blank 10 or the component 1 or to transfer it to another holder. Theblank 10 is only clamped into a holder once and can then be selectivelyor alternately machined subtractively or additively. Such machiningtools comprise a plurality of machining heads for this purpose of whichat least one is configured for subtractive production, that is, forexample, as a milling tool, and at least one is configured for additiveproduction, that is, for example, as an apparatus for laser build-upwelding. After the end of e.g. an additive machining step, the machiningtool autonomously changes the machining head and can subsequently carryout a subtractive machining step and vice versa. A particularly fast andhighly precise manufacture of the component 1 is hereby made possible.

Although the invention was explained with reference to the production ofan impeller 1, the invention is naturally not limited to such components1 or to their manufacture, but is rather suitable for a plurality ofother components 1, in particular for those components 1 in which atleast one inner passage 7 is provided whose geometry does not allow itto be worked out in a cutting or subtractive manner from a blank 10 witha justifiable effort.

The component 1 can also in particular be configured as a stator or as adiffuser of a rotary machine, with the rotary machine in particularbeing a pump or a turbine or a compressor or a compactor or an expander.

The inner passage can, for example, also be a cooling passage, e.g. in aturbine blade, for example a cooling air passage.

The invention claimed is:
 1. A method of manufacturing a component of arotary machine that has at least one inner passage extending from acenter up to a boundary surface of the component and is at least partlyclosed, the method comprising: providing a blank comprising the boundarysurface and a top surface; carrying out a first subtractive machining inwhich a part of the passage that at least comprises an opening of thepassage into the boundary surface as well as a cut-out in the topsurface is manufactured by machining production; and subsequentlycompleting the passage by build-up production on the blank such that thepassage has a first end in the center and a second end at the boundarysurface; wherein the at least one inner passage comprises a plurality ofinner passages of which each extends out of the center up to theboundary surface, each of a plurality of adjacent passages of theplurality of inner passages are partially separated by respective one ofa plurality of partition walls, a respective part of each respectivepassage of the plurality of inner passages is manufactured in the firstsubtractive machining of each passage of the plurality of innerpassages, each of the respective parts at least partially delimiting theopening of the respective passage into the boundary surface andpartially delimiting an opening of the respective passage into a cut-outin the top surface, and each of the partition walls is only completed bythe build-up production.
 2. The method in accordance with claim 1,wherein the carrying out the first subtractive machining includesproducing the cut-out in the top surface such that the cut-out extendsto the center.
 3. The method in accordance with claim 1, wherein the topsurface of the blank has at most one central opening before the firstsubtractive machining that is arranged in a radially inwardly disposedmanner such that a start of the passage disposed at the center isseparated from the central opening by a ring body in a completed stateof the component.
 4. The method in accordance with claim 1, wherein thefirst subtractive machining is carried out such that, after completionof the first subtractive machining, the top surface of the blank has acontiguous ring-shaped region adjacent to the boundary surface andcovering all the openings.
 5. The method in accordance with claim 1,wherein the build-up production takes place layer-wise.
 6. The method inaccordance with claim 1, wherein the build-up production comprises aplurality of additive machining to successively build up the component.7. The method in accordance with claim 6, further comprising at leastone further subtractive machining is carried out between the additivemachining.
 8. The method in accordance with claim 6, wherein a furthersubtractive machining is carried out between two additive machining. 9.The method in accordance with claim 1, wherein the completing thepassage by build-up production on the blank is a step in a process inwhich the component is built up element by element after the firstsubtractive machining.
 10. The method in accordance with claim 1,wherein the build-up production is carried out with the aid of a laser.11. The method in accordance with claim 1, wherein the component is animpeller or a stator or a diffuser of a rotary machine.
 12. The methodin accordance with claim 1, wherein the completing the passage bybuild-up production on the blank is a step in a process in which thecomponent is built up element by element after the first subtractivemachining.
 13. The method in accordance with claim 1, wherein thecomponent is an impeller or a stator or a diffuser of a pump, of aturbine, of a compressor, of a compactor or of an expander.